This invention concerns apparatus for use in conjunction with a drafting table for producing perspective drawings.
In producing a perspective drawing, straight lines traveling to the left side of the drawing are made to converge at a left vanishing point, and straight lines traveling to the right side of the drawing are made to converge at a right vanishing point. Such techniques impart a depth or three-dimensional effect to the drawing. In some instances, upright lines, instead of being drawn vertical to the horizon and parallel to each other, may be caused to converge at a vanishing point above or below the drawing. In those instances where the vanishing point is on the drafting table, a pin or nail can be inserted into the table and used as an abutment pivot point for a straightedge angled toward the drawing. In such manner, all lines drawn by the pivoted straightedge will converge at the vanishing point represented by the pin.
Such use of a pin, however, eventually defaces the surface of the drafting table. Devices have been disclosed in U.S. Pat. Nos. 4,075,762; 1,986,625; and elsewhere for adjustably establishing vanishing points which constrain a straightedge. Such devices, however, are of complex design and not universally suited for use as an attachment to a conventional drafting table. Certain devices of the prior art, by virtue of their specialized construction, further sacrifice ease of use or the speed with which straightedges can be accurately positioned by the draftsman for the drawing of lines.
It is accordingly an object of the present invention to provide an apparatus for attachment to a conventional drafting table for establishing vanishing points for the production of perspective drawings.
It is another object of this invention to provide apparatus of the aforesaid nature which provides adjustably positionable left side and right side vanishing points, and straightedges associated with said vanishing points.
It is a further object of the invention to provide apparatus as in the foregoing object which can provide upper and lower vanishing points and at least one straightedge which can be utilized in conjunction with either upper or lower vanishing point.
It is a still further object of this invention to provide apparatus as in the foregoing objects of simple and rugged construction which may be economically manufactured.
These objects and other objects and advantages of the invention will be apparent from the following description.